The U.S. Department of Energy as well as sustainable construction organizations and the like are pressing for the installation of dynamic daylighting and shading systems to improve energy efficiency in buildings. Innovations like that of the present invention are sorely needed to meet this need.
Various types of transparent and translucent glazing systems are available for the construction of horizontal, vertical and sloped glazing in skylights, roofs, walls, and other architectural structures designed to pass light for daylighting interiors or other purposes. When using such glazing systems, it is therefore desirable, in accord with sustainable construction criteria, to optimize the system's shading coefficient to reduce solar heat gain on hot summer days and during peak sunlight hours year round, while providing maximum light and solar heating on cold winter days and when it is otherwise needed or desired. It is also often desirable to control glare and direct sunlight in order to ensure the comfort of those who occupy the space exposed to the glazing system. If architects and space planners can be freed from the constraints of current light transmission control in horizontal, vertical and sloped glazing in skylights, roofs, walls, and other architectural structures, they will be able to more effectively address these shading requirements and meet sustainable construction criteria. Furthermore, these considerations apply as well to shading of open unglazed areas.
Indeed, if the level of light entering overhead large glazed as well as unglazed areas can be simply, efficiently, effectively and uniformly controlled without significant light leakage between, e.g., multiple adjacent light-controlling members, it will further enable architects and space planners maximize energy efficiency with aesthetic and sustainable designs. However, this requires light-controlling assemblies and sun control systems that can be dynamically controlled. For example, sun tracking control shading systems that can dynamically rotate light-locking members up to 360° to shade small or large glazed and open, unglazed areas to provide the desired uniform light level inside the space thereunder would be particularly desirable.
The known approaches to controlling the amount of light admitted through glazing systems—particularly on a large scale and in overhead, horizontal and sloped glazing applications—are limited and are generally unreliable, noisy and often difficult and expensive to construct, assemble on-site, maintain and service. Also, existing approaches suffer from non-uniform and excessive light leakage between adjacent light-controlling members which appears as an aesthetically undesirable series of often irregular bright lines. Additionally, although it is often desirable to retrofit light-controlling systems to already constructed glazing systems, this is not easily accomplished with any of the current light-controlling systems. There is therefore a substantial need for an economic and readily constructed and retrofitted light-controlling system that may be used for shading glazed areas of all sizes, including very large glazed areas. There is also substantial need for such light-controlling systems that can be easily assembled, maintained and serviced, in which the light is uniformly distributed across the glazed area, and in which light leakage is de minimis or eliminated and, where present, is kept to narrow and regular lines.
Prior approaches to controlling the level of light passing into architectural structures have included louver blind assemblies using pivoting flexible light-controlling members operable behind a window or sandwiched inside a chamber formed by a double-glazed window unit. Such louver blinds require substantial support of the flexible members which, additionally, must be controlled from both their distal and their proximal ends. Furthermore, louver blinds are difficult and expensive to assemble, apply, operate, maintain and replace, and cannot be readily adapted for use in non-vertical applications or in applications in which it is either desirable or necessary to control the flexible members from only one end. Louver blinds are particularly problematic when it comes to applications in which the installation requiring light-control or shading is very long, e.g., 10 ft., 20 ft., 60 ft. or more. In addition, dynamic control of louver blinds in large overhead shading applications is complicated, expensive, difficult to install and maintain, and often simply impractical. Furthermore, rotating louver blinds requires that the rotary force be applied to the top edge of the blinds. This is because louver blinds are flexible and rely on the force of gravity to hang vertically in the proper desired position and therefore cannot be rotated from their base. Thus, louver blinds cannot be used in generally horizontal overhead glazing application or in sloped applications, where rotation must be controlled from the base or proximal end and the force of gravity on non-vertical louver blinds would create untold complications and very non-uniform shading.
Other approaches to controlling the level of light passing through architectural structures have used motorized shades or drapery. These approaches are also problematic, particularly in the applications noted above where the glazing is large and would require lengthy shades or blinds, e.g., on the order of 10 ft., 20 ft., 60 ft. or more, since such large shades would be heavy, difficult to manipulate and maintain, and expensive. The mechanics of controlling and manipulating motorized shades or drapery of any size is quite complicated and therefore motorized shades and drapery are expensive and difficult to maintain. Also, it is not possible to achieve uniform light distribution across a wide glazed space with motorized shades or drapery.
U.S. Pat. Nos. 7,281,353; 6,499,255; and 6,978,578 provide other more recent approaches to addressing the challenge of providing dynamic daylighting and shading systems on a large scale and in overhead, horizontal and sloped glazing applications. These patents utilize a plurality of rotatably-mounted light-blocking tubular members having at least one portion that is substantially opaque and means for rotating the light-blocking members to block out varying amounts of radiation by varying the area of the opaque portions presented to the incoming light. In the systems described in the above three patents, the light-blocking members are combined in a series of adjacent segregated elongated tubular cells or mounted for rotation in individual or paired cross-members positioned between light transmitting panels. As an alternative to tubular members, a generally rigid opaque member may be used if fitted with rings spaced along this member. Indeed, even the tubular members may be fitted with such rings in order to facilitate tubular member rotation and to improve performance. Attachment of the rings requires notching of the generally rigid opaque member and is difficult and time consuming for both generally flat and tubular members. Also, the rings interfere with light-blocking and must be wide enough to accommodate longitudinal movement due to thermal expansion and contraction. Thus, determining the width and location of the rings and receiving notches is complex and, indeed, may require architectural approval before being implemented in custom applications, often making the use of such rings inconvenient and expensive.
In the system of the '578 patent, the centers of rotation of the light-blocking members do not remain in place as the light-blocking members are rotated resulting in increased torque and load on the motor and varying horizontal positioning of the light-controlling members. Since the light-controlling members often do not run true because they are inadequately restrained and therefore bend and snake about as they rotate, uneven and continuously varying spacing between adjacent members is produced with uneven light distribution and an unacceptable appearance of disarray of the radiation blocking members. When these light-controlling members are used in vertically oriented applications, the light-blocking members disengage from lower-cross-members and run far more untrue with even greater increases in the torque/motor load and irregular lateral movement. When they are used in applications calling for an inclined orientation, the light-blocking members tend to disengage from the lower cross members and rotate in an uncontrolled manner, rubbing against one another, resulting in increased friction and torque and producing problematic noise. Finally, in tests simulating the application of snow and wind loads, excessive friction is produced between the light-blocking members and the cross-members which could cause early failure.
The paired upper and lower cross members of the '353 patent solve the above problems. However, even this dual cross member design has drawbacks where rings and notching are used. Also, when this system is in the fully closed position, there is still more light leakage than is often desired.
While the designs provided by the above three patents nevertheless represent important advances in the art, they have another serious drawback. For these designs, the light-blocking components of adjacent tubular members cannot come sufficiently close to each other when the systems are in their fully closed configuration due to intervening structural features including the material between adjacent tubular cells in the '255 patent and the tube and ring walls in the designs of the '578 and '353 patents. Therefore total blackout or near total blackout light blocking cannot be achieved.